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Conventional propulsion systems are matched to meet power demand at designed operating points. Off-design conditions result in sub-optimal operation of prime movers since these are sized to cater for the peak power requirement. Hybridisation of power sources enables the advantages of separate sources to be exploited to best match actual operating conditions.In this work, permanent magnet machines are considered as auxiliary drives, providing propulsion at low ship speeds, complementing their use as shaft generators. Various topologies of auxiliary drive layout were analysed, considering different machine torque and speed ratings according to installation choice. As part of this study, the examination of auxiliary electrical drives was performed on a RoRo and tug with a view to assess reductions in exhaust gas emissions and fuel consumption. The two vessels were considered under typical operating scenarios. By means of simulation, the emissions and fuel consumption under auxiliary propulsion were quantified and compared to the contribution from the main engine. Significant emission savings were observed for the RoRo case particularly due to the use of cleaner fuel as a source. In the tug case, emission reductions could not be observed for this particular setup since the auxiliary drive system only adds additional inefficiencies in the propulsion system. Capital costs are significant, and the use of diesel fuel represents an increased cost. Yet if emission reductions are incentivised, auxiliary drives using permanent magnet machines are an attractive solution.